Ex-library books are ok according to the site so I think its okay as long as you didnt have requestor conditions. If you did then it was wrong to send, if you didn't have a RC you might want to consider one. If what you are describing are library stamps you can repost later for credit. If it makes you feel more comfortable PM the recipient before hand (but it is not required)

Here is a section from the help center (underling & bold of 2nd clause by me)

General remarks:

This is a used-book swapping site; books are not expected to be in like-new condition.

Older books may have some page yellowing or spine-creasing or dogeared pages; these are all OKAY.

Decirculated library books may have various markings and/or stamps inside or outside or on the page edges of the book; this is OKAY.

Bookcrossing books may have stickers or stamps or markings on the outside or inside covers or page edges of the book; this is OKAY.

Hardbacks do NOT have to include their dustjackets.

Audiobooks MUST be the original cassettes/CDs, but do NOT have to include the outer "box" that held the set.

Audiobooks must be playable.

There is an exception to general condition guidelines for textbooks; see below.

There is an exception to general condition guidelines for cookbooks; see below.

We do NOT have a place for members to describe the condition of a particular copy of a book.

ALL books on PBS are expected to be in "good, not excessively worn" condition

I agree, from your description it sounds like the book is postable as an ex-library book (which are presumed to have some stamps and stickers on them). Of course, if you have a no ex-library condition then it should not have been sent to you.

Carol, I have had the experience, like you, of marking a book "received" and then later finding a problem that wasn't noticeable at first (in my case it was some underlining that maybe the sender didn't even find, because it wasn't noticeable until you really got into reading the book). It IS frustrating! Your post is a good reminder that we should check our books carefully before logging them in (OR before sending them for that matter). I'm sorry you had a disappointing swap.

You've already received enough feedback to let you know that library books are fine here. I just thought I'd jump in an reassure you that there are people out there who are fine with receiving ex-library books. I'm one of them. :)

I recommend you place a requestor condition on your account if you don't want ex-library books in the future. You're likely to encounter this situation again. Many of the members here pick up books at the local Friends of the Library sales.